Brake control means



P 39, 1941 A. J. SO'RENSEN 2,257,311

BRAKE CONTROL MEANS Filed June 28, 1940 2 Sheets-Sheet 1 Main Reservoir Brake M A Travel I'Brward Reverse g6 68 1nd. 6| Lamp Slip Conrrolled Valve Device 36 Speed Conrrolld Valve Mech.

Direcrionol Repemer lNVENTO R ANDREW J. 50REN5EN BY ATTORNEY Patented Sept. 30, 1941 BRAKE CONTROL MEANS Andrew J. Sorensen', Edgewood, Pa", assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application .lune 2c, 1940, Serial No. 342,941

(01. sea-21) 33 Claims.

This invention relates to brake control means for vehicles, such as railway cars and trains, and has particular relation to brake control apparatus adapted to automatically reduce the degree of application of the brakes on the vehicle as the speed of the vehicle reduces and at the same time effective to rapidly reduce the degree of application of the brakes. associated with individual wheel units or groups of wheel units in the event that one or more of the wheel units of a group begin to slip, in order to prevent the sliding of the wheels.

As is well known to those skilled in the art, the coefiicient of friction between the brake shoes and the rim of a railway car wheel increases as the speed of rotation of the wheel decreases.

Accordingly, if a given fluid pressure is maintained in the brake cylinder operating the brake shoes, the degree of application of the brakes on the wheel automatically increases as the speed of the car decreases. If the degree of application of the brakes increases sufficiently as the speed of the vehicle reduces so as to cause the adhesion or rollingfriction between a wheel and the rails or road. surface on which the wheel rolls to be exceeded, the wheel promptly decelerates at an abnormally rapid rate to a locked or non-rotative condition and slides.

In the. present application, the term slide refers to the dragging of a vehicle wheel along a rail or road surface in a locked or non-rotative condition. The term slip refers to the rotation of a vehicle wheel at. a speed less than a speed corresponding to vehicle or car speed at a given instant. Thus when a vehicle wheel decelerates at anahnormally rapid rate toward a locked or non-rotative condition, the wheel is said to slip but the wheel does not slide until it is actually locked. The distinction between these two terms should be borne in mind.

Operators of railway cars and trains customarily manually reduce the degree of application of the brakes, as the speed of the car or train reduces, in order to prevent the degree of application of the brakes increasing. sufiiciently with the increase in the coefficient of friction between the brake shoes and the car wheels resulting from the. reducing speed to cause sliding of the wheels. More recently, especially on highspeed passenger trains, a mechanical speed governor has been employed for the purpose of reducing the degree of application of the brakes automatically and independently of any action by the operator as the speed of the car or train reduces asto prevent sliding of the wheels. It will be understood that sliding of railway car wheels is objectionable because of the development of fiat spots, on the wheels which necessitate repair or replacement of such wheels.

Notwithstanding the manual or automatic reduction in the degree of application of the brakes as the speed of a car or train reduces, sliding of the car wheels nevertheless sometimes occurs because of the non-uniformity of rail conditions i and thus of the adhesion between the rails and wheels, It has accordingly been proposed to pro vide devices, either of a mechanical or an electrical nature, which are sensitive only to a slipping condition of a wheel for automatically eif ecting a rapid reduction in the degree of the brakes associated with a slipping wheel or wheel unit so as to cause the slipping wheel or wheel unit to cease deceleration and begin acceleration thereof back toward a speed corresponding to car speed before the slipping wheel or wheel unit can decelerate to a locked or non rotative condition and slide.

It has further been proposed to provide appara QIlS responsive to the pressure in the brake cylinders for causing the rapid reduction of pressure in the brake cylinders, initiated in response to the operation of the wheel-slip responsive de-. vices, to continue until the pressure in the brake cylinders is reduced below a certain low value so as to insure the acceleration of the slipping wheel or wheels back toward a speed corresponding to car speed and at the same time inhibit the reapplication of the brakes by resupply of fluid under pressure to the brake cylinders until the slipping wheel or wheels have been restored fully to a speed corresponding to vehicle speed. It will be understood that the time required for a slipping wheel to be restored to a speed corresponding to car speed, although variable, is less than the time ordinarily required for the pressure in the brake cylinders to be reduced below the certain low value. Thus thereduction of pressure in the brake cylinders associated with slipping wheels continues and the resupply of fluidunder pressure to the brake cylinders and the consequent reapplication of the brakes does not occur until after the slipping wheels are restored fully to a speed corresponding to car speed.

In the copending application Serial No. 306,878 of Donald L. McNeal and John Canetta, filed November 30, 1939, and assigned to the assignee of this application, there is disclosed a brake in order to maintain a safe limit of application so 55 control equipment for vehicles, such as railway cars and trains, in which electrical apparatus responsive to the speed of rotation of one car wheel or wheel unit and electrical apparatus responsive to the rate of rotative deceleration and acceleration of all the car wheels or wheel units automatically control the degree of application of the brakes on a car or train in accordance with the speed of the car or train and, at the same time, effect the rapid reduction in the degree of :application of the brakes associated with a slipping wheel unit to prevent the sliding of the wheels.

My present invention is designed to accomplish in general the same objectives as are accomplished by the equipment disclosed in the abovementioned copending application. In the de-' velopment of a practical system for actual commercial installation I have, however, been con-- fronted with numerous problems in the carrying out of these objectives and have accordingly devised a novel and improved apparatus diifering specifically from that disclosed in the copending application and adapted to function satisfactorily in commercial service.

For example, in the above-mentioned copending application an electrical governor in the form of a magneto or direct-current generator driven according to-the speed of rotation of a wheel unit of a Vehicle supplies a voltage which is substantially proportional to the speed of rotation of the wheel unit, and consequently to the speed of travel of the car or vehicle, and a plurality of voltage-responsive relays of the neutral type are arranged so .as to be respectively operative in response to different successively spaced voltages, corresponding to different speeds of the vehicle, for effecting the corresponding control of the degree of application of the brakes in accordance with the speed of the vehicle. I have found that the characteristics of the neutral type of relay are such as to. render difficult the accurate and uniform response of relays at given vehicle speeds. I have found it desirable to provide voltage-responsive relays of the'so-called unidirectional type, that is, responsive to flow of current in only one direction through the operating winding thereof, for the reason that they are more sensitive and more accurate in operation. The provision of voltage-responsive relays of the uni-directional typeinvolves the necessity for control apparatus responsive to. the direction of rotation of the vehicle wheels and consequently of the direction of travel of the vehicle for insuring the proper direction of flow of current through the operating windings of the relays notwithstanding reversal of the direction of rotation of the wheels and consequently of the direction of travel of the vehicle.

It is accordingly an object of my invention to provide a novel speed-controlled brake equipment for vehicles including a so-called electrical governor and voltage-responsive relays of the unidirectional type, together with directional control apparatus for insuring operation of the voltage-responsive relays notwithstanding reversal of the direction of rotation of the vehicle wheels and consequently of the direction of travel of the vehicle.

ernor, manual control means was provided in the copending application whereby an adequate degree of braking could be secured.

It is another object of my present invention to provide means for automatically insuring an adequate degree of application of the brakes in the event that the electrical speed governor should fail, thereby obviating need for the human element required with the apparatus shown in the copending application.

It is another object of my invention to provide brake control apparatus of the type indicated in the foregoing objects and further characterized by apparatus sensitive to a slipping condition of individual wheel units of a group for rapidly reducing the degree of application of the brake associated with all the wheel units of that group to prevent sliding thereof.

Another object of my invention is to provide equipment of the character indicated in the foregoing'object and characterized by a novel arrangement for insuring reduction of the pressure in the brake cylinders associated with the slipping wheels until the pressure in the brake cylinders reduce below a certain low value.

The above objects and other objects of my invention which will be made apparent hereinafter, are attained by means of one embodiment of a brake control equipment shown in Figs. 1 and2 of the accompanying drawings when placed in side-by-side relation.

DESCRIPTION OF EQUIPMENT ((1) Introduction Before proceeding to a description of the equipment, it should be understood that the equipment as shown does not correspond exactly to the commercial brake control equipment to which my invention pertains and in which it is employed. My invention is intended to be applied to the type of brake control equipment for high speed passenger trains referred to as the HSC type of equipment and described in various instruction pamphlets of The Westinghouse Air Brake Company, one of which is Instruction Pamphlet 5064, Sup. 13. It should be understood, therefore, that while I have represented a simplified form of pneumatic control apparatus whereby the control ,of the brakes associated with the car wheels is eifected under the control of the operator, my invention is not limited in its application to the specific type of pneumatic operator-controlled brake apparatus shown.

The equipment shown in the combined Figs. 1 and 2 is that for two wheel trucks 1 I and I2. Ob-, viously, in the case of articulated cars employed in the modern high speed streamlined trains one wheel truck may support adjacent ends of two cars. It should be understood, therefore, that although the equipment is hereinafter described as for a single car of the non-articulated type in which each car is independently supported by wheel trucks at opposite ends thereof, the equipment may be employed for cars of the articulated type.

In the subsequent description of my invention, it will be assumed that movement of the vehicle in the left-hand direction corresponds to forward travel of the vehicle and that movement of the vehicle in the right-hand direction corresponds to reverse travel of the vehicle. This is indicated by the arrows and legend at the top of each figure. The truck II will hereinafter according- 1y be designated the front wheel-truck and truck l2 will be designated the rear wheel-truck.

The wheel-trucks II and I2 may be the conventional' type of four-Wheel truck onrailway cars, each truck having a trailing and a leading wheel-unit respectively comprising a pair of wheels rolling on opposite track rails and connected by an axle to which they are fixed. It willbe apparent that in the drawings only one wheel l3 of each wheel-unit of each truck is shown. It should be understood that my invention is applicable to railway locomotives of the electric or Diesel type and that the wheel-units shown may be the wheel units of the locomotive or power unit.

While not shown, it will be understood that the brakes associated with the wheels l3 may be of the conventional clasp type operated through conventional brake rigging by brake cylinders l 5. While any desired number of brake cylinders may be provided, for each wheel truck, I have shown only one brake cylinder for each wheel-unit, that is, for each pair of axle-connected wheels. Thus, in the case of a car wheeltruck, there are two brake cylinders for each truck, shown in a vertical line above the corresponding truck.

Fluid under pressure is supplied to the brake cylinders, IE to effect application of the brakes associated with the wheels l3 and released from the brake cylinders l5 to effect the release of the brakes under the control of the operator of the vehicle through the medium of suitable apparatus shown, in simplified form, as comprising a socalled control pipe IS the pressure in which is controlled by means of an operator-controlled brake valve device H. The brake valve H is of well-known self-lapping type having an operating handle Ila, fixed to a rotary operating shaft through the medium of which the self-lapping valve mechanism is operated. The source of fluid under pressure for charging the control pipe I6 is a reservoir l8, hereinafter referred to as the main reservoir, which is suitably charged to a normal pressure, such as one hundred pounds per square inch, by means of a fluid compressor not shown. Main reservoir I8 is connected. to and constantly charges to a correspending pressure a pipe hereinafter designated the supply pipe I9.

In the case of a train of cars, the control pipe It and supply pipe l9 may comprise sections extending from end-to-end of each car and connected by suitable hose couplers 20at the opposite ends thereof between the cars. 2! are provided, in the usual manner, at each end of each pipe to close the end of the pipe section on a car when desired.

The brake valve I! is connected to the control pipe IS and the supply pipe [9 by branch pipes y'f are in open position and that the brake valve ll controls the pressure in the control pipe [6.

With the brake valve handle Ila in its normal brake release position, the self-lapping valve mechanism of the brake valve I! is conditioned to efiectthe exhaust of. fluid under pres- Angle cocks When it is desired to control 4;

sure from theclontrol pipe l6 through an exhaust port and pipe 25 of the brakevalve. When the brake valve handle llanis shifted in one direction in a horizontal plane out of its brake release position into a so-called' application zone, the

self-lapping'valve mechanism of the brake valve I! is operated to, cause fluid under pressure to be supplied from the supply pipe I9 and the connected main reservoir l8 to control pipe Hi to charge it to a pressure corresponding substantially to the degree of displacement of the brake valve handle out of its, normal brake release position. If the pressure in the control pipe 16 tends to reduce for some reason, such as leakage, the self-lapping mechanism of the brake valve automatically operates to maintain a pressure in the control pipe corresponding to the position of the brake valve handle.

(5) Speed-controlled valve mechanism 27 A so-called speed-controlled valve mechanism 27 of well-known construction is provided to supply fiuid at a pressure depending upon the pressure in the control pipe l6, but having variable ratios thereto depending upon the speed of travel of the vehicle, to effect the application of the brakes. is described in detail and claimed in Patent No. 2,140,624 to Ellis E. Hewitt.

Essentially, the speed-controlled valve mecha nism 27 is made up of three sections referred to hereinafter respectively as the relay valve section 28, the diaphragm section29 and the mag- ".et valve section 30. i

The relay valve section 28 comprises: a supersensitive high capacity self-lapping relay valve mechanism of well-known type which is operated in response to an operating force exerted by fluid pressure responsive means in the form of four coaxially spaced unconnected movable abutments' or diaphragms of progressively increasing or decreasing effective pressure areascontained in the diaphragm section 29. i i

The four diaphragms may have any desired ratio of effective pressure areas relative to one another but for illustrative purposes it will be assumed that they have effective pressure areas of ten, eight, six, and four units of area respectively. The diaphragms are arranged with the largest diaphragm adjacent the relay valve section 28 sothat one face of the largest diaphragm is subject tothe pressure in a pressure chamber of the relay valve section 28 and the opposite face is subject to the pressure of fluid in a chamber formed between the largest diaphragm and the next succeeding diaphragm of eight units of area. Due to the coaxial spaced relation of the .diaphragrns, similar chambers are formed between each successive pair of diaphragrns. A chamber is also formed at the outside face of the smallest diaphragm.

Fluid under pressure is supplied at all times to the chamber at the outside face of the small est diaphragm, and selectively to the three chambers between successive pairs of diaphragms under the control of three magnet valve devices 3 IE, 35M, and 35L of the magnet valve section 30, from a branch pipe 16a of the control pipe E6.

The operating force for the relay valve section 28 accordingly depends not only. upon the unit pressure of the fluid supplied to the chambers between the diaphragms but also the area of the particular diaphragm which is effective to exert the operating force.

When the magnet winding of magnet valve A valve mechanism of this type 3|H is deenergized it causes fluid under pressure-to be vented to atmosphere from the chamber between the largest'diaphragm and the next succeeding smaller diaphragm; and when the magnet winding of magnet valve 3IH is energized, it causes communication to be established through which fluid under pressure is supplied from the branch pipe 3a to said chamber.

When the magnet winding of magnet valve SIM is deenergized, it causes fluid under pressure to be vented to atmosphere from the chamber formed between the two intermediate diaphragms; and when the magnet winding of magnet valve 3| M is energized, it causes communication to be established through which fluid under pressure is supplied from the branch pipe 16a to said chamber.

When the magnet winding of magnet valve 3|L is deenergized it causes communication to be established through which fluid under pressure is supplied from the branch pipe I60; to the chamber between the smallest diaphragm and the next succeeding larger diaphragm; and when the magnet winding of magnet valve 3|L is energized, it causes fluid under pressure to be vented from said chamber.

It will accordingly be seen that when the magnet windings of magnet valves 3|I-I and MM are deenergized and that of the magnet valve 3IL is energized, all of the chambers between the diaphragms are vented. The chamber at the outside face of the smallest diaphragm being constantly connected to and charged with fluid un' der pressure from the branch pipe [6a, the operating force for the relay valve section 28 is accordingly the unit pressure of the fluid supplied from the control pipe It to said chamber multiplied by the area of the smallest diaphragm.

Upon the application of the operating force thereto, the relay valve section 28 operates to supply fluid under pressure from a branch pipe |9a ofthe supply pipe I9 to a pipe 35 leading to two slip-controlled valve devices 36, one of which is provided for each wheel truck [I and I2 respectively. As will hereinafter appear, the slipcontrolled valve devices 36 are relay valve devices which normally operate to supply fluid under pressure from the branch pipe 19a of the supply pipe to a pipe 31 leading to the brake cylinders of the corresponding wheel truck, in accordance with the pressure of the fluid delivered to the pipe 35.

The pressure delivered by the relay valve section 28 of the speed-controlled valve mechanism 21 to the pipe 35 is effective in the pressure chamber of the relay Valve section 28 on one side of the largest diaphragm to exert a force in opposition to' the force exerted by the effective diaphragm to lap or close off the supply of fluid under pressure to the pipe 35. Accordingly, the pressure established in the pipe 35 when the smallest diaphragm is effective to operate the relay valve section depends upon the ratio of the effective pressure area of the smallest and largest diaphragms. If, as previously assumed, the largest and the smallest of the diaphragms have effective pressure areas of ten and four units of area respectively, it will be seen that the selflapping relay valve'section 28 will establish a pressure in the pipe 35 which is forty percent of that in the control pipe when the smallest diaphragm is efiective.

When the magnet windings of all of the magnet valves 3|H, MM, and 31L are deenergized,

fluid'under pressure is supplied not only to the chamber at the outside 'of the smallest diaphragm but also to the chamber between the smallest diaphragm and the larger diaphragm.

Accordingly, the fluid pressure forces on the smallest diaphragm are balanced Whereas the unbalanced force on the next to the smallest diaphragm is effective to operate the relay valve section 28. In such instance, assuming an effective pressure area of six units for the diaphragm effective in this instance, it will be seen that the relay valve section 28 establishes a' pressure in the pipe 35 which is sixty percent of that established in the control .pipe I6.

When the magnet valve 3IM only is energized, fluid under pressure is sup-plied to the chamber at the outside of the smallest diaphragm, to the chamber between the smallest and the next larger diaphragm, and also to the chamber between the two intermediate diaphragms. Thus the fluid pressure forces on the smaller two diaphragms are balanced and the unbalanced force on the next to the largest diaphragm (of eight units of area) is effective to operate the relay valve section 28. In such case, the relay valve section 28 establishes a pressure in the pipe 35 which is eighty percent of the pressure established in the control pipe l6.

When the magnet windings of magnet valves NH and MM are energized while that of the magnet valve 3|L is deenergized, fluid under pressure is supplied to the chamber at the outer face of the smallest diaphragm and to all of the chambers between successive pairs of diaphragms. In such case, the fluid pressure forces on all the diaphragms except the largest diaphragm are balanced so that the unbalanced force on the largest diaphragm is efl'ective to operate the relay valve section 28. The relay valve section 28 is thus operated to establish a pressure in the pipe 35 which is substantially equal to the pressure in the control pipe It.

It will thus be seen that by selectively energizing or deenergizing the magnet windings of magnet valves 3ll-I, 3|M, and 31L of the speedcontrolled valve mechanism 21 in different combinations, the pressure supplied to the slip-controlled valve devices 36 and correspondingly to the brake cylinders l5 may be varied with respect tr; the pressure established in the control pipe Each of the magnet valves 3lH, 31M, and 3|L is efiective to vent fluid under pressure from the diaphragm chamber controlled thereby at a controlled rate so that when the combination of magnet valves in effect is changed so as to effect a reduction of the pressure of fluid supplied to pipe 35 to a lower percentage of the pressure established in the control pipe it, such reduction is not instantaneous but at a controlled rate. The reason for this will be made apparent hereinafter.

(c) Slip-controlled valve devices 36 Each of the slip-controlled valve devices 36 is made up of three sections, namely an intermediate pipe bracket section 39 to opposite faces of which are secured a self-lapping relay valve section 4|, of the type described in Patent 2,096,491 to Ellis E. Hewitt, and a magnet valve section 42 having a magnet valve of standard double beat type including a magnet winding 43.

The pipes I911, 35 and 31 are connected to the pipe bracket section 39 and lead through appropriate passages to parts of the valve device 36 in the manner presently to be described.

When the magnet winding 43 of the magnet valve section 42 is deenergized, the magnet valve establishes communication through which fluid under pressure from the pipe 35 flows to a pressure chamber at one side of the operating abutment or piston of the relay valve section 4 I. The relay valve section M accordingly operates to supply fluid under pressure from the branch pipe l9a of the supply pipe IQ to the pipe 3'! leading to the brake cylinders I5, the pressure etablished in the brake cylinders I corresponding substantially to the pressure established in the pipe 35. Upon the reduction of the pressure in the pipe 35, the relay valve section 4| operates to vent fluid under pressure from the brake cylinders [5 through an independent exhaust port not visible in the drawings to effect a reduction of the pressure in the brake cylinders l5 corresponding to the reduction of the pressure in the pipe 35. Thus the relay valve section 4! is effective to establish a pressure in the brake cylinders l5 which at all times corresponds to the pressure in the pipe 35 as long as the magnet winding 43 of the magnet valve section 42 is deenergized.

When the magnet winding 43 of the magnet valve section 42 is energized, the communication between the pipe 35 and the pressure chamber at one side of the operating piston of the relay valve section H is closed and an exhaust communication established through which fluid under pressure from the said pressure chamber is vented to atmosphere at a rapid rate. Accordingly, whenever the magnet winding :3 of the slip-controlled valve device 38 is energized, the relay valve section ti operates to rapidly reduce the pressure in the brake cylinders I5 controlled thereby and to continue such reduction as long asthe magnet winding 43 is energized. It will thus be apparent that the slip-controlled valve devices 36 control the pressure of the fluid in the brake cylinders E5 of the corresponding wheeltruck only whereas the speed-controlled Valve mechanism 2? is effective to control the pressure of the fluid in the brake cylinders for both wheel trucks I! and i2.

(d) Pressure switches 44c, 44f. and 44 Associated with the control pipe and each of the brake cylinder pipes 37 leading to the brake cylinders of each wheel truck are fluid pressure controlled switch devices 440, Mi and HT respectively, hereinafter called pressure switches. These pressure switches may be of any suitable well-known type, preferably the snap-acting type in which a movable contact member is snapped into and out of engagement with a pair of stationary contact members in response to an increase of a control pressure supplied to the pressure switch above a critical pressure and reduction below such critical pressure, respectively. In the case of the pressure switch 450, the movable contact member thereof is actuated to its closed position in response to an increase of pressure in the control pipe 16 above a certain low pressure, such as five pounds per square inch, and is restored to its open position in response to a decrease of pressure in the control pipe below such pressure. In the case of each of the pressure switches 44] and Mr, the movable contact member thereof is. actuated to closed position in response to an increase of pressure in the corresponding brake cylinders above a certain low pressure, such as five pounds The function of the pressure switches c, 441,

and 441 will be made apparent hereinafter.

(e) Electrical control apparatus Associated with one or more or, as indicated in the drawings, all of the wheel units of the vehicle are magnetos or generators 48 of the direct-current type, the rotary armature of the generators being driven in accordance with the rotative speed of the corresponding wheel units and adapted to produce a voltage at the brush terminals 49 and 55 of the generators which is substantially proportional to such rotative speed. These generators 48 may be mounted in any suitable manner as, for example in the journal casing at the end of an axle connecting a pair of wheels with the rotary armature of the generator disposed in coaxial relation to and coupled to the end of the axle.

Aplurality of relays 52L, 52M, and 52H, hereinafter referred to as the speed relays, are provided and controlled the voltage supplied by one of the generators, shown as the generator 48 associated with the left-hand or leading wheel-unit of the wheeltruck ll. As will hereinafter appear, the speed relays 52L, 52M, and 52H are adapted to function in a cooperative and coordinated manner to effect the selective energization and deenergization of the magnet valves 34H, EIM, and ML of the speed-controlled valve mechanism 22'.v

A plurality of relays 53a, 53b, 53c, and, 53d hereinafter referred toas the slip relays are provided, one for each of the wheel units respectively, and arranged to operatein a manner presently to be described in response to the rate of change of voltage delivered by the generators 48 of the corresponding wheel units. The slip relays 53a and 53b corresponding respectively to the two wheel-units of the wheel-truck H are effective to control energization of the magnet winding 43 of the slip-controlled valve device 33 corresponding to the wheel-truck II. In a similar manner, the, slip relays 53c and-53d are effective to control energization of the magnet winding 43 for the slip-controlled valve device 36 corresponding to the rear wheel-truck l2.

As will be made more clear hereinafter, the speed relays and the slip relays are of the so called uni-directional type responsive only to the flow of current throughan operating winding thereof in one direction and non-responsive to the flow of current through the operating Winding in the opposite direction. It is necessary, therefore, because of the reversal of polarity of the brushterminals 49 and 50 of the generators 48 due'to reversal of the direction of rotation of the wheels with reverse travel of the vehicle to provide a directional control apparatus for insuring the uni-directional flow of current through the operating winding of the speed relays and slip relays. I accordingly provide, according to my invention, a pair of socalled directional relays 54 and 541" and a'pair of so-called directional-repeater or repeater relays 55 and 55r. The directional relays 54) and Share of the uni-directional type operatively responsive only to flow of current through an operating winding thereof in one direction and non-responsive to the flow of current through the winding in the opposite direction.

It will be observed that the speed relays, the slip relays, and the directional relays are all unirespectively according to directional relays and as a practical matter are of substantially identical construction and design. The response of the relays to different voltages is provided for by means of adjustable resistors external to the relays in the manner hereinafter to be pointed out.

Each of the uni-directional relays comprises two operating windings a and b respectively and a varying number of contact members depending upon the function of the relay.

The operating windings of the directional relays .54 and 541' are connected in series relation across the brush terminals of one of the generminal 50 is of negative polarity. Conversely,

when the vehicle travels in the reversedirection, it will be assumed that the polarity of the brush terminals will be reversed, that is, that the brush terminal 50 will be of positive polarity and the brush terminal 49 of negative polarity.

The operating windings a and b of the directional relays 54] and 54T are so connected in the energizing circuit therefor that only one of the relays is responsive to a flow of current in one direction whereas only the other relay is responsive to flow of current in the circuit in the opposite direction. Assuming a flow of current from the positive brush terminal to the negative brush terminal of generator 48 it will, therefore, be

seen that when the vehicle travels in the forward direction, the flow of current in the circuit of the directional relays is such as to cause an operative response only of the directional relay 54 Conversely, when the vehicle travels in the reverse direction, and the current to the directional relay windings is reversed, the directional relay 54r only is operatively responsive.

The rheostat B is so adjusted that when the speed of the vehicle exceeds a certain low speed such as eight miles per hour, the current energizing the windings of the directional relays becomes suilicient to cause an operative response of the contact members to a picked-up position, the contact members being maintained in a picked-up position as long as the speed of the vehicle exceeds such speed and being restored to the dropped-out position thereof whenever the vehicle speed reduces substantially below the critical operating speed or current.

Each of the directional relays 54 and 541 is provided with two front contacts 0 and d and a back contact 6. It will be understood that, as employed herein, a front contact is one which is in open position when the relay is droppedout and which is actuated to a closed position when the relay is picked-up, whereas a back contact is one which is in closed position when the relay is dropped-out and is actuated to open position when the relay is picked-up.

The contacts 0 of the two directional relays 54 and 541 are connected in parallel relation in a circuit including an indicating lamp 6| which is located in a convenient position adjacent the brake valve H and visible at all timesby the operator of the vehicle. Since onelor other of the directional relays 541 and 541 will always be picked-up when the vehicle is traveling at a speed above the critical pick-up speed of the directional relays if the generator 48 supplying the current for energizing the relays is operating properly, it will be seen that the resulting illumination of the indicating lamp 6| will serve as an indication to the operator that the corresponding generator 48 is functioning properly. It is important that the operator be apprised of the proper operating condition of the generator 48 associated with the speed relays 52L, 52M, and 52H in order that he may know in advance if he may depend upon the proper response of the speed relays.

The circuit for energizing the indicating lamp 6| extends from the positive terminal of a source of current such as a storage battery 64 by way of a so-called positive battery wire 65, a branch wire I66, in parallel through one or the other of the contact members contact 0 of the directional relays 54 and Mr, a wire 61 including the filament of the indicating lamp 6|, and a wire 68 to the negative terminal of the battery 64. The battery 54 is preferably the usual carlighting battery provided with suitable charging equipment (not shown) for maintaining the battery charged. The terminal voltage of the battery 64 may be any suitable desired value such as 64 or 32 volts.

The contact d of the directional relay 54 controls a circuit for energizing the operating winding of the repeater relay f to cause it to be 0perated to a picked-up position.

Ina similar manner, the contact (1 of the directional relay 541' controls a circuit for energizing the winding of the repeater relay 551' to cause it to be operated to a picked-up position. The circuit for energizing the winding of the repeater relay 55f includes the back contact e of the directional relay 541". Conversely, the circuit for energizing the winding of the repeater relay 55r includes the back contact 6 of the directional relay 54 The contacts of the two directional relays 54f and 541* are thus so interlocked that only one of the repeater relays 55;

and 551" can be operatively picked-up at one time. The circuit for energizing the respective windings of the repeater relays 55 and 551 will be hereinafter traced in detail in connection with the operation of the equipment but it may be flows through the windings of the repeater relays 55 and 551' always in the same direction. Repeater relays 55] and 551" are of the neutral type because relays of the neutral type cost less than relays of the uni-directional type and because they are adapted to be operated by higher current than the uni-directional relays and thus provide adequate power for operating the large number of contacts required for effecting the reversing control of the circuits including the speed relays and the slip relays.

I Each of the repeater relays 55] and 551' is provided with two front contacts a and b and five so-called front-and-back contacts 0, d, e, ,f, andg. The front-and-back contacts engage a,-

lower stationary contact in the dropped-out position. thereof and an upper stationary contact in the picked-up position of the relay.

The contact a of each of the repeater relays 5.51, dr is a so-called stick contact for establishing a holding circuit to maintain the winding of the relay energized independently of the corresponding directional relay 54] or 541' once the energizing circuit for the repeater relay winding is established. The contacts b of the repeater relays 55f and 551- are arranged in parallel relation so that when either of the directional relays ispickedeup, the positive battery Wire 85 is connected to a wire 12 for a purpose hereinafter to be made apparent.

The back-and-front contacts c and d of the two repeater relays 55f and 552' are arranged in such manner as to reverse the connections between a pair of bus wires 19 and 80, across which the operating winding a of each of the speed relays 52L, 52M, and 52H is connected, and the brush terminals 49 and 50 of the generator 48 associated with the left-hand wheel unit of the front wheel truck H in response to a reversal of polarity of the brush terminals so as to maintain a uniform polarity of voltage on wires 79 and 8t and thus a uni-directional flow of current through the operating windings aof the speed relays. These contacts 0 and def the repeater relays f and 557 also serve at the same time to a reverse the connections of the operating coil a of the slip relay 53a to the brush terminals 49 and 5B of the same generator.-

Each pair of the back-and-front contacts e, f, and g of the repeater relays 55] and 551' cooperate respectively to reverse the connections of the operating winding a of one of the slip relays 53b, 58c, 53d to the brush terminals 49 and 59 of the generator for the corresponding wheel units.

It will be observed that two back-and-front contacts cand d of each of the repeater relays 55 and 55'! are employed in controlling the application of generator voltage to the speed relay buswires l5 and Bil, whereas only one back-anda front contact of each of the directional relays 55,1 and 551- is employed to provide directional control for the winding a of the slip relays 53b, 53c, and 53d. The reason for the extra set of back-and-front contacts in the case of the bus wires l9 and 85 is to prevent any possibility of short-circuiting the armature winding of the generator 4S supplying energizing current to the directional relays 54 and 542'. If, while one of the repeater relays 55f or 551* is being picked-up, a

short-circuit is established across the armature winding of the generator 43 supplying current to the winding of the directional relays 54 and 55?, the directional relay tending to pick-up will immediately drop out thus causing the corresponding repeater relay to drop-out immediately. This operation will repeat itself indefinitely. In order to prevent such an occurrence, therefore, and to insure the proper operation of the directional relays 54 and 541, the two pairs of contacts 0 and d are employed. The generators 48 not having directional relays 54f and 541' dependent thereupon may be momentarilyshort-circuited when one or the other of the repeat-er relays 55f an 557' is being picked-up because no undesirable result occurs.

Referring now to the speed relays 52L, 52M,

and 52H, the respective operating windings a of the relays are connected across the bus wires respectively; a portion of each of the resistors 81a,

19 and in series with a rheostat or adjustable resistor Bla, tilt, and Bio respectively. The resistors Bla, 8th, file are adjusted to different resistancesso as to cause pick-up of the speed relays 52L, 52M, and 52H at different voltages across the bus wires 19 and 80. For example, these resistors may be adjusted to have values of three thousand ohms, six thousand ohms, and ten thousand ohms respectively. It will thus be seen that although the windings of the speed relays 52L, 52M, and 521-1 may be identical in design, the relays themselves are oper atively picked-up at different voltages. For example, when the voltage across the bus wires 19 and 80 exceeds a value corresponding to a vehicle speed of twenty miles per hour the current through the winding a of the speed relay 52L becomes sufiicient to cause an operative response or pick-up of the relay. Similarly, when the,

voltage impressed on the bus wires 19 and increases above a value corresponding to vehicle speed of forty miles per hour, the current through the winding a of the relay 52M becomes sufiicient to cause an operative response or pick-up of the relay. In a similar manner also when the voltage across the bus wires 79 and 88 increases above a value corresponding to a speed of seventy miles per hour, the current through the winding a of the speed relay 52H becomes sufficient to cause an operative response or pick-up of the relay.

It is characteristic of electrical relays that when the movable armature actuating the contacts of the relay is shifted to a picked-up posi- 0 tion, the air-gap between the armature and the usual stationary core of the relay is so reduced that a lesser current is required to maintain the armature in picked-up position than was original- 1y required to cause it to be picked-up. For this reason, the contacts of the relay do not drop-out at the same voltage at which they were pickedupbut remain picked-up until the control voltage of the relay has dropped a substantial.

amount below the voltage required to pick the relay contacts up.

In order to causethe contact members of the speed relays 52L, 52M, and 52H to pick-up and drop-out at substantially the same voltage impressed on the windings a of the relays and, therefore, at substantially the same vehicle speed,

8"), and Me isshunted when the associated speed relay is dropped-out and this portion of the resister is cut into the circuit with the winding a of the corresponding speed relay by removing the shunt connection thereon when the corresponding relay is picked-up. The manner in which this shunt connection on a portion of the resistors sw, BIZ), and 810 is established and removed will be described presently.

Associated with the speed relays 52L, 52M, and 52H are two additional or auxiliary relays 82 and 83. The relays 82- and 83 are similar in that both relays have two windings designated respectively the upper winding a and the lower winding b. The relay B2 is providedwith three front contacts designated 0, d, and 6 respectively and with one back contact designated f. The relay 83 is provided with one'front contact 0, four back contacts designated d, e, f, and g respectively, and a so-called transfer contact h of the back-and front type.

One terminalof the upper winding a of relay 82 is connected by a wire 85 to one terminal of the winding 1) of speed relay 52H and by a branch wire 86 of wire 85'to one terminal of the winding b of the speed relay 52L. The other terminal of the upper winding a of the relay 82 is connected by a wire 81 to the contact h of the relay 83. The contact h of the relay 83 in the dropped-out position thereof engages a lower stationary contact that is connected by a wire 88 to the terminal of the, winding 1) of the speed relay 52L opposite to the said one terminal. In its pickedup position the contact h of relay 83 engages an upper stationary contact that is connected by a wire 89 to the terminal of winding b of speed relay 52H opposite the said one terminal thereof. It will thus be seen that when the contact h of relay 83 is in its dropped-out position, the upper winding a of. the relay 82 and the winding 1) of the speed relay 52L are connected in series relation while the circuit for the windingv b of the speed relay52I-I is open. Conversely, when the contact h of the relay 83 is in its icked-up position, the circuit for the winding b of the speed relay 52L is open and a circuit is established including the upper winding a of the relay 8 2 and the windingbof the speed relay 52Hin series relation. The purpose of these COIlIlECtlOIlS will be made apparent presently.

One terminal of the lower winding 1) of the relay 82 is connected by a wire 92 including an adjustable resistor 93 to the wire 12. The other terminal of the lower winding 17 of the relay 82 is connected by a wire 94 to the contact e of relay 83 and to the single front contact of speed relay 52H, and'by a branch wire 95 to the contact f of the relay 83. In its dropped-out position, the contact e of the relay 83 engages a stationary contact member which is connected by a wire 96, hereinafter referred to as the negative battery wire, which is connected by the pressure switch'dllc to the Wire 68, in turn connected to the negative terminal of the battery 64.. As-' suming that the pressure switch 440 is closed and that one or the other of the directional-repeater relays 55f or 55r is picked-up, a circuit is accordingly established for energizing the lower winding b of the relay 82. This'circuit extends from the positive terminal of the battery 64 by way of the positive batterywire 65, one or the other of the contacts b of the repeater'relays 55] or 551" depending upon which is picked-up, the wire 12, resistor 93, wire92, lower winding 1) of the relay 82, wire 94, contact e of the relay 83, negative battery wire 96, pressure switch 440, and wire 68 to the negative terminal of the battery 64.

It will thus be seen that whenever the pressure switch 440 is closed, as it is normally whenever an application of the brakes is initiated, and assuming that one or the other of directional-repeater relays 55] or 551 is picked-up indicating that the vehicle is traveling in excess of a speed requisite thereto, the contacts of the relay 82 are accordingly actuated to the picked-up position thereof.

The contact member of the relay 82 is effective in its picked-up or closed position to establish the previously mentioned shunt connection around the portion of the resistor-8m associated with the winding a of the speed relay 52L. This shunt circuit includes a back contact (2 of speed relay 52M so that the pick-up of relay 82 cannot establish the shunt connection around the portion of resistor Bla unless speed relay 52M is dropped-out. The reason for this will be explained hereinaften The contact f of the relay 82 is effective in its dropped-out position to establish a shunt connection'arounda portion of the resistor 8Ic associated with the winding a of the speed relay 521-1 and, upon the actuation of the contact 1 to its picked-up or open position, this shunt connection is removed or opened.

The contact d of the relay 82 is effective when actuated to its picked-up or closed position to establish a circuit from the wire 12 for eifecting energization of the magnet winding of the magnet valve 3 [L of the speed-controlled valve mechanism 21. This circuit includes the back contact g of the relay 83 so that if the contact 9 of relay 83 is in its picked-up or open position, the actuation of the contact d of relay 82 to its picked-up or closed position is ineifective to establish the energizing circuit for the magnet winding of magnet valve ML.

The contact e of the relay 82 functions in cooperative serial relation with the contact 0 of the relay 83 to establish a circuit for energizing the magnet winding of the magnet valve 3IH of the.

speed-controlled valve mechanism 21. The contact c of the relay 83 functions, in and of itself, to control a circuit for energizing the magnet winding of the magnet valve 3IM of the speedcontrolled valve mechanism 21.

The contact d of the relay 83 is eifective, in its dropped-out or closed position, to establish a shunt connection around a portion of the resistor 8|b associated with the winding 12 of the speed relay 52M and, when actuated to its picked-up or open position, removes or opens this shunt connection.

The single front contact of the speed relay 52L is interposed in a wire 98 one end of which is connected to the wire 92 at a point between the resistor 93 and the lower winding b of the relay 82 and the other end of which is connected to the stationary contact associated with the contact I of the relay 83. Thus, when the speed relay 52L is picked-up, the contact thereof establishes a short-circuit connection around the lower winding 1) of the relay 82, thereby causing the contacts of the relay 82 to drop-out. The resistor 93 is effective, while the winding 1) of relay 82 is shortcircuited, to prevent short-circuiting of the battery 64.

Due to the dying away of the magnetic flux in the core of the relay 82 as a result of the shunting of the lower winding 1) thereof, a momentary voltage is induced in the upper winding a of the relay 82 which causes a current to flow in the previously described circuit including the winding 1) of the speed relay 52L in a direction to assist the upper winding a, to effect the actuation of the contact of the speed relay 52L to its closed position. Positive operation of the contact of the speed relay 52L is accordingly effected and a fluttering or hesitant operation thereof prevented.

When front contact 0 of the speed relay 52M is actuated to its picked-up or closed position, it establishes a circuit for energizing the lower winding b of the relay 83, thereby causing the contacts of this relay to be actuated to their picked-up position. The circuit for energizing the lower winding 2) of relay 83 extends from the positive battery wire by way of a branch wire I91, the front contact 0 of the speed relay 52M, lower winding b of the relay 83 and a resistor I02 to the negative battery wire 95. Resistor I02 is provided for limiting the current energizing the winding b of the relay 83 to its proper value.

' The upper winding a of auxiliary relay 83 is constantly connectedin a loop circuit with the winding b'of speed relay 52M. When the circuit for energizing the lower winding b of the relay 83 is established, the build-up of magnetic flux in the core of the relay causes a momentary voltageto be induced in the upper winding a and a current accordingly flows through the lower winding b of the speed relay 52M in a direction to assist the winding a thereof to effect the closure of the contact of the relay 52M without fluttering or hesitation.

The contact d of the relay 83 is effective when actuated to its picked-up position to open the shunt connection around a portion of the resistor 8lo associated with winding a of the speed relay 52M. Thus, Whenever the speed relay 52M is picked-up, additional resistance is cut into the circuit of the upper Winding a thereof for the reason previously stated.

When the contact h of the relay 83 is actuated to its picked-up or open position, it disconnects the winding 2) of speed relay 52L from the upper winding a of relay 82 and connects the winding 12 of speed relay 52H thereto, as previously described. I

The contact of relay 83 is effective, when actuated to its picked-up or open position, to remove the shunt connection around the lower winding 1) of the relay 82. Accordingly, when the single front contact of the speed relay 52H is actuated to its picked-up or closed position, it establishes a circuit for energizing the lower winding 1) of the relay 82. The contact of the relay 82 is accordingly actuated to its picked-up or open position to open the shunt connection around a portion of the resistor 8lc associated with the winding a of the speed relay 52H for the reason previously stated. The build-up of the magnetic flux in the core of the relay 82 in response to the energization of the lower winding b induces a momentary voltage in the upper winding a of the relay 82 which is eifective by Way of the circuit previously traced including transfer contacth of the relay 83 to cause current to flow through the lower winding b of the speed relay 52H in a direction to assist the upper winding a to effect the positive actuation of the front contact thereof to a closed position without hesitation.

The above description of the cooperative relation of the speed relays 52L, 52M, and 52H and the relays 82 and 83 is deemed suificient for present purposes for the reason that further details of the operation will be brought out more clearly in connection with an assumed operation of the equipment.

Referring now to the slip relays 53a, 53b, 53c, and 5311, these relays are adapted to be responsive to the rate of change of voltage across the brush terminals 49 and 50 of the corresponding generators 48 by interposing in series relation with the upper winding (1 thereof across the brush terminals 49 and 50 of the corresponding generator a condenser I of suitable capacity. It will accordingly be seen that when the voltage at the brush terminals of one of the generators 48 increases, due to an increase in speed of the vehicle or the rotative acceleration of a slipping wheel unit back toward a speed corresponding to car speed, current flows in the circuit in one direction through the upper winding a of the corresponding slip relay to charge the correspondingcondenser I05, the currentvarying in degree according to the rate of increase of-generator voltage. It will be apparent that the higherthe rate of increase of voltage across the brush terminals of a generator 48, the greater is the .erator.

9 instantaneous difference between the voltage to which the condenser I05 is charged and the voltage across the brush terminals of the gen- Consequently, the charging current in the circuit will be substantially proportional to the rate of acceleration of the corresponding wheel unit.

Conversely, when the wheels of a wheel unit decelerate, the voltage across the brush terminals of the corresponding generator 48 decreases at a corresponding rate. The greater the rate of rotative deceleration of the vehicle wheels, the greater is theinstantaneous difference between the voltage to which the condenser I05 is charged and the voltageacross the brush terminals of the generator. Accordingly, the current discharged in the circuit from the condenser in a reverse direction to the charging current is substantially proportional to the rate of deceleration of the vehicle wheels.

It should be understood that this type of electrical apparatus for recognizing or measuring the rate of acceleration or deceleration of a rotating element is not, in itself, my invention.

The upper winding a of each of the slip relays 53a, 53b, 53c, and 53d is so connected in the circuit across the brush terminals of the corresponding generator 48 that the relay is picked-up only in response to a condenser discharge current and is not picked-up in response to a condenser charging current. Furthermore, the winding 0, of each of the slip relays is so designed that unless the current discharged from the condenser in the corresponding circuit exceeds a certain value corresponding to a rate of rotative deceleration of the wheels of the corresponding wheel unit which occurs only when the wheels slip, for example ten miles per hour per second, the single front contact of the relay is not operated to its picked-up or closed position.

As previously stated, the slip relays 53a, 53b, 53c, and 5301 are uni-directional relays similar to a polarized relay in that they are responsive or non-responsive depending upon the direction of flow of current through the operating winding thereof and similar to a neutral relay in that when the current in the proper direction to cause pick-up of the relay reduces below a certain value, the contact member of the relay is restored to its dropped-out position. Inorder, therefore, to prevent the drop-out of the contacts of the slip relays when the rate of rotative deceleration of the corresponding wheel unit decreases below a slipping rate, the windings b of the relays are utilized as holding windings. As will be explained more fully hereinafter, the holding winding b of only two of the slip relays, namely, relays 53b and 53d, are utilized.

The circuit for the holding winding 1) of the relay 53b is established whenever the contact of either of the relays 53a and 53b is actuated to its picked-up or closed position. This holding circuit, as will be explained hereinafter, includes the pressure switch 44f associated with the brake cylinders of the corresponding wheel truck I I and the magnet winding 43 of the magnet Valve section 42 of the slip-controlled valve device 36 of the corresponding truck. In a similar manner, the holding circuit for Winding b of relay 53d, including magnet Win-ding 43 of slip-controlled valve device 36 for wheel truck l2 and pressure switch 44, is established by actuation of the contact of either of the relays .530 or 53d to its picked-up position. It will thus be seen that once the holding circuit for the holding winding 12 of one of the slip relays is established, it is main- OPERATION or EQUIPMENT (a) Conditioning of equipment Let it be assumed that the main reservoir 18 is charged to the normal pressure carried therein, and that the car having the equipment shown in Figs. 1 and 2 is at a standstill with the brake valve handle lid in its brake release position establishing atmospheric pressure in the control pipe l6 preparatory to applying propulsion power to the propulsion means of the vehicle. Since the car is stationary, the generators 48 associated with the wheel units are not producing anyvoltage andconsequently the directional relays 5d and 541* are dropped out. Since the contact of both directional relays i) and Mr is in open position, the circuit previously traced for energizing the indicating lamp ti is interrupted and consequently, the lamp is dark, At the same time, due to the fact'that atmospheric pressure is established in-the control pipe It, the pressure switch 440 is in open position thereby interrupting the connection between the negative battery wire 96 and the negative terminal of the battery 65 and preventing'possible drainage of current from the battery while the car is standing still or out of service. The pressure switches M7 and 14T associated with the brake cylinders 15 are likewise in open position because fluid under pressure is released from the brake cylinders.

Since the directional relays 5'2) and 541* are both dropped-out, the directional repeater relays 55] and 551 are correspondingly both droppedout. Accordingly, the bus wires l9 and 85] on which the speed relays 52L, 53M, and 52H operate are disconnected from the corresponding generator 48 as are also the win-dings a of all of the slip relays 53a, 53b, 53c and 53d.

Now let it befurther assumed that the operator of the car operates a suitable propulsion controller' (not shown) supplying power to the propulsion means (not shown) of the vehicle and that the car begins to' accelerate in a forward direction;

When the speed or" the car exceeds a relatively low speed, such as eight miles per hour, the directional relay f is picked-up. The indicating lamp Si is thus immediately illuminated due to the completion of the energizing circuit therefor by'the closure of the contact. 0 of the directional The closure of the contact at of the directional relay '54 is ineffective to cause energization of the winding of the repeater relay 55] because of the fact that the pressure switch Me is in open position and prevents the completion of the energizing circuitfor the winding of the relay 55]; This will be made clear hereinafter'when the circuit for energizing the winding of the relay 55 is described. V

The fact that the" directional relay Ed is picked-up however indicates that thegenerator i8 is producin'g voltage, in a proper manner as indicated'by the illumination of the indicating 'released, the windings a of the relays 52 L,-52 M,

. the directional relay'54f.

(6) Application of brakes: speed-control operation Let it now be assumed that the car has been accelerated to and is traveling at a speed such as eighty miles per hour and that the operator desires to bring the car to a stop. To do so, the operator first shuts oh the propulsion power and then shifts the brake'valve handle Ha into the 35 at a pressure depending upon the combinatlon of magnet valves 3|H, 31M, and ML in effect at the particular speed, as will be explained presently. The fluid under pressure supplied to the slip-controlled-valve devices 36 causes operation thereof to supply fluid under pressure from the supply pipe l9 and branch pipe l9a to the associated brake cylinders l5 to effect application of the brakes associated with the wheels 13 of both wheel trucks i I and "l 2.

When the pressure in the control pipe 16' V exceeds the pressure requisite thereto, namely flve pounds per square inch, the pressure switch 30 is operated to closed position and establishes a circuit for energizing the winding of the re peater relay 55 This circuit extends from the positive'terminal of the battery 64 by way of the positive battery wire 65, a branch wire Ill including the resistor H, back contact 6 of the directional relay 541', a wire I i 2, winding of relay 55 a wire H3, front contact 11 of the directional relay 5 1 wires H4 and H5, negative battery wire 9%, closed pressure switch 440, and wire 68 back to the negative terminal of the battery 64. -The contact a of the relay 55 is effective in its picked-up or closed position 'to establish a circuit for maintaining'the windingof the relay 55] energized independently of the contact (1 of It will be apparent that this is the case because the contact a of the relay 55 is connected in parallel'wi-th' the contact 12 of the directional relay 54 e t The contact 17 of repeater relay 55 is effective in its picked-up or closed position to com in series with the upper winding of the speed relay 52L;

The contacts 0 and 12 oftherepeater relay 55]- are efiective when actuated to the picked-up-positions thereof to establish theconnections between the bus wires Hand and the brush ter-- minals 49 and 50 of thegenerator 46 on which the directional relays 54 and 551 operate. With a the brush terminals- 49 and 50 of the generators 48' respectively of positive and negativepolarity;

as previously assumed for the forward travel of the car, the bus wires I9 and 88 are connected respectively to the brush terminals 49 and 50 and are thus respectively of positive and negative polarity. Since the generators are already producing a voltage at the brush terminals corresponding to the speed of the car, the voltage across the bus wires I8 and 88 accordingly buildsup to a corresponding value. The speed relays 52L, 52M, and 5211 are thus sequentially pickedup as the voltage across the bus wires I9 and 80 builds-up because flow ofcurrent through winding a of these relays from wire I9 to wire 80 is in the proper direction to pick-up the relays.

As previously indicated, when the speed relay 52L is picked-up the contact thereof establishes a short-circuit by way of the contact 1 of the relay 83 around the lower winding 1) of the relay 82 and relay 82, therefore, drops-out. At the same time, the momentary voltage induced in the upper winding a of the relay 82 assists the winding a of speed relay 52L to positively close its contact. Contact of relay 82 is effective when thus restored to its dropped-out or open position to remove the shunt connection around the portion of resistor 8Ia, thus inserting this additional resistance in the circuit of windinga of speed relay 52L.

When the speed relay 52M is picked-up, the front contact 0 thereof establishes the circuit,

previously traced, for energizing the lower winding 1) of the relay 83 and the contacts of relay 83 are accordingly actuated to their picked-up positions. As previously explained, the voltage momentarily induced in the upper winding a of the relay 83 due to energization of winding 7) energizes the winding 20 of the speed relay 52M toassist the winding a thereof to effect positive closure of its contact. Back contact d of speed relay 52M is effective in its picked-up or open position to prevent the establishment of the shunt connection around a portion of resistor 8 la when relay 82 is subsequently picked-up as presently described. i

1 The back contact 1' of relay 83 is effective when actuated to its picked-up or open position to interrupt the short-circuit connection around the lower winding 1) of relay 82, but due to the fact that the backcontact e of relay 83 isalso actuated at the same time to its picked-up or open position, the circuit for energizing the lower Winding 1) of relay 82 is interrupted. Thus, when pick-up of speed relay 52M is effected, the relay 82 remains dropped-out.

When the single front contact of the speed relay 52H is actuated to itspicked-up or closed position, it reenergizes the lower winding 1) of the relay 82 because of the fact that the shortcircuit around this winding was previously opened due to opening of the back contact of the relay 83 inresponse to pick-up thereof.

Contact 0 of relay 82 is'not effective at this time when actuated to its picked-up or closed position to shunt the portion of resistor 8Ia because back contact d of speed relay 52M is in open position, and prevents it from doing so. It is possible to omit contact 12 of speed relay 52M from; the shunt circuit around a portion of resistort Ia but it is preferable to include this contact d of speed relay 52M in order to prevent the possible undesired fiuttering of the contact of speed relay 52H. If contact 0 of relay 82 were permitted to establish the shunt connection around the portion of resistor 8 I a in response to pick-up of speed relay 52H, the increasedload on the generator 48 controlling the speed relays might cause sufiicient drop in the terminal voltage thereof that speed relay 52H woulddrop-out immediately after being picked-up. This would in turn cause relay 82 to drop-out. Speed relay 52H would thus instantly pick-up again and the fluttering operation would continue until the terminal voltage of the generator increased sufficiently to maintain the speed relay 52H pickedup notwithstanding the shunting of the portion of resistor 8| a. I

The contact 01 of the relay 82 is non-efiective in its picked-up or closed position to produce any result at this time because of the back contact g of the relay 83 being simultaneously in its open position.

. Contact 0 of the relay 83 is effective in its picked-up or closed position to establish a circuit for energizing the magnet windingof the magnet valve 3IM of the speed-controlled valve mechanism 21. This circuit extends from the positive terminal of the battery 64 by way of the positive battery. wire 65, a branch wire I2I, contact :0 of the relay 83, a wire I22, magnet winding of. the magnet valve 3IM, a wire I23, negative battery ,wire 98, closed pressure switch 440, and wire 88 back to the negative terminal of the battery 64.

Contact e of relay 82 is efiective in its closed or picked-up position jointly with the contact 0 of the relay 83. in its picked-up orclosed position to establish a circuit for energizing the magnetwinding of the magnet valve 3IH of the speed-controlled valve mechanism 21. This circuit extendsfrom the positive terminal of the battery 64 by way of the positive battery wire 65, branch wire I2I, contact 0 of relay 83, wire I22, contact e of relay 82, a wire I25, magnet winding of the magnet valve 3IH, a wire I25, negative battery wire 96, closed pressure switch 840, and wire 68 back to the negative terminal of the battery 64.

I It will thus be seen that with the car traveling at a speed of eighty miles per hour, which is typical of the operation at speeds in excess of seventy miles per hour, the magnet windings of the magnet valves 3IH and 3IM are energized whereas the magnet winding of the magnet valve 3IL is deenergized. As previously explained, the speed-controlled valve mechanism 21 is therefore effective to supply fluid to the pipe 35 at a pressure equal to the pressure established in the control pipe I6. The slip-controlled valve devices 36 are accordingly effective to cause fluid to'be supplied to the brake cylinders I5 of the corresponding wheel trucks at a pressure corresponding to the pressure supplied .into the pipe 35.. If, therefore, a pressure of fifty pounds per square inch is established in the control pipe It as previously assumed, it will be seen that an equivalent pressure is established in the brake cylinders I5.

When the speed of the vehicle reduces slightly below seventy miles per hour, corresponding to the critical pick-up point of the speed relay 52H, the contact of the relay 52H is restored to its open position interrupting the circuitfor energizing the lower winding 19 of the relay 82. The contacts of relay 82 are accordingly restored to their dropped-out position.

Due to the dying-away of flux in the magnetic core of relay 82 upon the deenergization of winding b' thereof, a voltage is momentarily induced in winding a of relay 82 which causes flow of current through the winding b of speed relay 52H inv a' direction to oppose the efiect of the current in the winding a. of relay 52H, thus causing the contact ofspeed relay 52H to be. positively restored to'its open position without fiuttering'or hesitation.

As. previously indicated, the contact of the,

relay 82' is 'efiective in. its dropped-out position toshunt. a portion. of the resistor Bic in the circuit of the winding a of the speed relay 52H. The restoration or" contact. {2 of the relay 82' to its dropped-out or open position is without. effect at this time because the shunt connection around a portion of the. resistor Bid in. the circuit' of the winding a of the speed relay 52L is already open at back contact cl of speed relay 52M. The

restoration of the contact d of the relay 82 to its. open position is obviously without effect at this time.

The contact e of the relay 82 is effective when restored to its dropped-out. or open position to interrupt the circuit, previously traced, for energizing' the magnet winding of the magnet valve 3IH of the speed-controlled. valvemechanism 2T, As previously explained, the valve mechanism 21 is accordinglyconditioned by virtue of the .fact

that only themagnet winding of the magnet.

therefore, that when the speed of the vehicle reduces below seventy miles per hour, the pressure in the brake; cylinders 15 is automatically: reduced't'o eighty percent of fifty pounds per square inch or forty'pounds per square inch.

Thus, .without any act. of the operator; the 'degree ofap pli-cation of thebrakes associated with the wheels;..of the vehicle is reduced in proportion to the. reduction in the degree of fluid pressure supplied to the brake cylinders.

In, the case of a train of cars of the non-articulated type, no undesired slack action can result. due to reduction of the degree of application of the; brakes by speed-controlled valve mechanism 2:? because the rate of reduction is controlled.

lWhen the speed of the car reduces in response to the continued application of the brakes to a speed slightly below forty miles per hour, corresponding to the critical pick-up point of the speed relay 5 2M, the contacts of the relay 52M are restoredto their dropped-out positions. Contact c of relay 52M accordingly interrupts the energizing circuitfor the. lower windingzh of the relay 83 which correspondingly drops-out. Due to. the dying-away of the magnetic flux in the core associated with the windings of the relay 9:3, a voltage is induced momentarily in the upper winding u thereof which causes a flow of current in the winding 1) of the speed relay $2M in a direction opposing the effect of the current in winding 0.: of the relay 52M, thereby causing the contacts of the relay 52M to be positively operated to: their dropped-out positi'on'sgwithout fluttering. The restoration. of contact d? Qfspeedrelay 52M *to its dropped-out or .Qlflifid position is without effect at'this time because contact c of'relay 82 is inrits openposition and; thereby prevents. the'establishment of the shunt connection around a portion of resistor 3.1a. due. to drop-out of speed relay 52M. As previously indicated, the restoration of the contact (1' of the relay 8.3- to its dropped-out or closed position following deenergization of wind-- ing 1) thereof restores. the shunt connection around aportion of the resistor Bib-in the circuit. of the winding a, of. the speed relay 52M. Transfer contact h of the relay 83 is efiective in its dropped-out position to reconnect the upper winding a of relay 82 in series relation with winding bot speed relay 52L.

Back contact e of relay 83 is effective in its droppedrout or closed position. to establish a circuit tending to. energize the lower winding 1) or the. relay 82 but the back contact f of relay 83 is effective in its dropped-out or closed position in cooperation. with the still-closed contact of the speed relay 52L to, at the: same. time, shunt the winding 2) of the relay 82 and prevent its energization. Thus, when the speed relay 52M is: dropped-out, the relay 82 remains dropped-out.

, Contact, 0. of relay 83 is effective when restored to its dropped-out or open positionto interrupt the circuit for energizing the windingoithe magnet valve 3lM of the speed-controlled valve mechanism 27. At the same time, since the contact. 03' of, relay 82 is in its'dropped-out or open position, the restoration of the contact g of relay 8 3 to its dropped-out or closed position is without efiect. f

It will thus be seen that when. the speed relay 52M is dropped-out, the auxiliary relays 82 and 8-3. are positioned so as to efiect d-eenergizationof the magnet windings of all of the magnet valves. 3:H, MM and 31L of the speed-controlled valve mechanism 21. As previously explained, the

valvemechanism 21 is accordingly effective to reduce at a controlled'ratethe pressure supplied thereby to the; pipe 35 to a. value which is sixty percent ofthe pressure established in the con.-- trolpipe Hi. 'The slip-controlled valve devices 36 associated with both wheel trucks accordingly operate to correspondingly reduce the pressure of the associated brake cylinder l5. Assuming a. pressure of fifty; pounds per square inch to re-' main in the control pipe, it will be seen that when the speed of the vehicle reduces below forty miles. per hour in: response to the application of thebrakes, the speed-controlled valve mechanism. efi'ects a reduction of the pressure in. the brake; cylinders 15 at a controlled rate to a value which is sixty percent of fifty pounds per square inch or thirty pounds per square inch.

When the speed of a. car reduces below twenty 7 relay 52L drops-outto its open position, thereby interrupting the, shunt connection including'backf contact I of relay 83 around the lower winding 11 of the relay azp-Accordinglndue to the fact:

that the. back. contact e of relay 8:3 establishes a a circuit for energizing the winding 19 of relay 82st;

this time, the winding 2) of relay '82 is energized,

and the contacts of relay 82 are accordingly actuated to their picked-up positions.

The momentary voltage, inducedsin the upper winding (1 of the relay 82, as a result of the.

be positively actuated to outafluttering.

, The contact of the relay 82 is efiective at this time when actuated to its picked-up or closed position to shunt a portionof the resistor 81a associated with the Winding a of thespeed relay 52L because back contact d of speed relay 52M is inlitsclosed position. The relay 52L is thus properly conditioned for a subsequent pick-up at the proper speed.

Contact d of the relay 82 is effective, when actuated to its closed position, to establish the circuit for energizing the magnet winding of the magnet valve 31L of the speed-controlled valve mechanism 21. This circuit extends from the positive terminal of the battery 54 by way of the positive battery wire 65, contact b of the directional repeater relay 55], wire 12, contact d of the relay 82Qwire l3], back contact g of the relay 83, Wire I32, magnet winding of the magnet valve 3IL of the speed-controlled valve mechanism 21, wire I33, negative battery wire 96, closed pressure switch 440, and wire 68 back to the negative terminal of the battery 64.,

Due to the front contact 0 of relay 83 being in its dropped-out or open position at this time, the actuation of the contact e of relay 82 to its its open position withpicked-up or closed position is ineffective to,

cause energization of the'magnet winding of the magnet valve 3IH of the valve mechanism 27. The magnet valve 3IM also remains energized due to the open position of the contact 0 of the relay 83.

'It will thus'be seen that, when the speed of the car reduces below twenty miles per hour, the speed relay 52L drops-out and thereby operates through the auxiliary relays 82 and 83 to cause energization of the magnet winding of only the magnet valve 3 IL of the valve mechanism 21. As previously indicated, the valve mechanism 21 accordingly operates to further reduce the pressure of the fluid supplied to the pipe 35 at a controlled rate to establish a pressure therein which is only forty per cent of the pressure established and maintained in the control pipe I6. Assuming that a pressure of fifty pounds per square inch is maintained in the control pipe IS, the reduction in the speed of the car below twenty miles per hour is eifective to cause reduction of the pressure supplied by the valve mechanism 21 to the pipe 35 to forty percent of fifty pounds per square inch or twenty pounds per square inch.

Theslip-controlled valve devices 36 for both wheel trucks H and I2 accordingly operate in response to the reduction of the pressure in the pipe 35 in the manner justdescribed to correspondingly reduce the pressure in the brake cylinders to twenty pounds per square inch, thereby again further decreasing the degree of application of the brakes.

No further change in the condition of the speed-controlled valve mechanism 21 occurs as the car reduces toward zero speed or stopped.

position and accordingly the pressure which remains established in the brake cylinders asthe speed of the vehicle reduces from twenty miles per hour to zero speed will remain forty per cent of that established in the control pipe Hi. It will be apparent that such is the case because, although the directional relay 54 (or 541*) drops out when the speed of the car or train reduces somewhat below eight miles per hour, the corresponding repeater relay 551 (or 55r) remains stuck-up due to the holding circuit therefor established by its own front contact a as previously described. Thus, lower winding b of relay car reduces from a speed of twenty miles per hour to zero speed and does not become deenergized until such time as the brakes are released by the operator and the pressure switch 440 correspondingly opened, as hereinafter described, to

interrupt the holding circuit for the repeater relay (or 551) r If desired, the operator, of the vehicle may operate the brake valve handle Ila to reduce the pressure in the controlpipe l6 as the vehicle reduces in speed, although the automatic reduction of the pressure in the brake cylinders by operation of the speed-controlled valve mechanism 21 is intended to make this unnecessary. Obviously, however, if the operator does vary the pressure in the control pipe it during an application of the brakes While the vehicle is reducing in speed, the degree of application of the brakes will vary correspondingly althoughthe ratio between the pressure established in the brake cylinders and that in the control pipe will remain unchangedfor a given speed range as determined by the speed relays'52L, 52M and 52H;

After the car comes to a complete stop, the operator may increase the pressure in the control pipe 15 to a maximum pressure to correspondingly increase the degree of application of the brakes and thereby provide adequate braking to hold the vehicle at a standstill on any grade occurring under service conditions. Obviously, the increase in the degree of application of the brakes after the vehicle has come to a stop in no way operates to cause sliding of the wheels so that such increase in the degree of application of the brakes may be made safely.

It was assumed above that the application 0 the brakes was initiated at a time that the car was traveling at a speed of eighty .miles per hour. Obviously, if the application of the brakes is initiated while the car is traveling at any speed between forty and seventy miles per hour, such as sixty miles per hour, only the speed relays 52L and 52M would be picked-up and the speed relay 52H would remain dropped-out. Accordingly, the speed-controlled valve mechanism 21 will, in such case, be initially conditioned to cause energization of only the magnet winding of the magnet valve 3|M. Thus, the pressure initially established in the pipe 35 and correspondingly in the brake cylinders I5 will be eighty percent of that established in the control pipe Hi. Thereafter, as the car speed reduces successively below forty and twenty miles per hour, the speed-controlled valve mechanism 21 is successively conditioned to reduce the pressure in the brake cylinders to sixty and forty percent of that in the control pipe 16.

If the application of the brakes is initiated when the car is traveling at any speed between twenty and forty miles per hour, such as thirty miles per hour, only the speed relay 52L will be picked-up and consequently the valve mechanism 21 will be conditioned in response to the deenergization of the magnet windings of all of the magnet valves thereof to produce a pressure in the pipe. 35, and correspondingly in the brake cylinders l 5, which is sixty percent of that established in the control pipe l6. Thereafter as the speed of the car reduces below twenty miles per hour, the speed-controlled valve mechanism is conditioned to reduce the pressure in the brake cylinders to forty percent of that in the control pipe I6.

If the application of the brakes is initiated while the car is traveling at a speed below twenty miles per hour and in excess of eight miles per hour, all of thespeed relays 52H, 52M, and 52L will be dropped-out and the valve mechanism 21 will be correspondingly conditioned by the energization of the magnet winding of only the magnet valve 3IL to establish apressure in the pipe 35' and in the brake cylinders 15 which is forty per cent of that established in the control pipe I 6. The pressure in the brake cylinders may be varied thereafter by operation of the brake valve ll but the percentage of the pressure in the brake cylinders relative to the pressure in the control pipe will be maintained thereafter until the car is completely stopped and then also as long as the brakes remain applied, as previously explained.

If the car is traveling less than eight miles per hour, or if the generator 48 supplying voltage to the bus wires 19 and 8!! fails to deliver voltage thereto at any speed While the brakes are released, the arrangement of the directional relays 543 and 541" and. the repeater relays 55 and 551' which I have provided is automatically eifective, in response to initiation of a brake application, to cause the speed-controlled'valve mechanism 21 to be conditioned to cause the fluid pressure established in the brake cylinders to be sixty per cent of the pressure established in the control pipe. Failure of the speed-control generator 48 to supply voltage to the bus wires 19 and 80 may be caused by a short-circuited or a burntout armature winding.

It will be apparent that if the one or the other of the directional. relays 54 and 541 are not picked-up for whatever reason, the corresponding repeater relays 55] and 551* cannot be pickedup. If both of the repeater relays 55f and 551" are dropped-out, then the connection between the positive battery wire 65 and the 'wire 12 is interrupted due to the contact I) of both repeater relays being in dropped-out or open position. Accordingly, even though the back contact 6 of relay 83 is in its dropped-out or closed position, the lower winding b of relay 82 cannot be energized and the relay contacts correspondingly actuated to their picked-up position. With the front contacts 12 and e of the relay 82 in their respective dropped-out or open positions, therefore, the circuits for energizing the magnet windings of the, magnet valves ML and 3|H of the valve mechanism 2'! are both interrupted. At the same time, relay 83 is dropped-out because the speed relay 52M is dropped-out, and consequently the front contact of relay 83 is effective in its dropped-out or open position to prevent the energization of the magnet winding of the magnet valve 31M and also of the magnet valve 3 IE of the valve mechanism 21.

It will thus be seen that when an application of the brakes is initiated at a time that the car is traveling at a speed less than eight miles per hour, or at any speed while the speed-control generator 48. fails to supply voltage, valve mechanism 21 will be conditioned automatically to cause the pressure of the fluid supplied to the brake cylinders to be sixty per cent of that established in the control pipe I6- Ordinarily, the operator of the car or train will make only a light application of the brakes if the car is traveling at a speed less than eight miles per hour and thus the fact-that brake cylinder pressure is sixty per cent of the pressure in the control pipe will not cause an unduly severe degree of application of the brakes so as to produce possible sliding of the wheels. There is, moreover, a distinct advantage in having the pressure in the brake cylinders be sixty per cent of that in the control pipe in the event that the speed-control generator 48 fails to deliver voltage for the reason that it is intended that, assuming a maximum pressure to be established in the control pipe 16, a pressure in the brake cylinders which is sixty percent of such pressure will effect a brake application which will be equivalent to a normal braking ratio of one hundred and fifty percent. The term braking ratio. as used in'this instance refers, in the customary manner, to the ratio between the number of pounds exerted on all the brake shoes by the brake cylinders in relation to the weight of the car. Since a braking ratio of one hundred and fifty percent is considered adequate to bring a vehicle to a' stop in a reasonably safe stopping distance, it will be seen that even if the automatic speedcontrolled equipment fails to function in its intended manner, an adequate and safe degree of application of the brakes may nevertheless be obtained automatically upon initiation of an application of the brakes.

If the speed-control generator 48 supplying the repeater relay 55 (or 551*) has been pre-' viously picked-up and remains stuck-up as previously described so that the relay 82 remains picked-up While the relay 83 is dropped-out. Thus, the circuit previously described including the front contact d of relay 82 and the back contact g of relay 83 for energizing the magnet winding of the magnet valve ML of valve mechanism 21 will be establishedand the valve mechanism 21 thereby conditioned to cause apressurc to be established in the brake cylinders which is forty per cent of that in the control pipe. Even in such case, the braking effect which may be produced is entirely adequate to stop the car or train although the stopping distance may be lengthened somewhat with respect to the usual stopping distance.

(0) Application of brakes:

operation anti-wheeZ-slz'ding of the brakes, regardless of the particular speed range in which the car is traveling, the wheels of the trailing wheel unit of the truck I2 begin to slip. In such case, the contact of the slip relay 53d is actuated to its picked-up or closed position, thereby establishing a circuit for energizing the magnet winding 43 of the magnet valve sec tion 42 of the slip-controlled valve device 36 corresponding to the rear wheel truck I2 which circuit at the same time constitutes a circuit for energizing the holding winding 12 of the slip relay 53d. This circuit extends from the positive terminal of the battery 64 by way of the positive battery wire 65, a branch wire I 4|, winding 1) of the slip relay 5312, a wire I42, contact of the relay 53d, a wire I43 including in series relation therein the closed pressure switch 441' and the magnet winding 43 of the slip-controlled valve device 36 for the rear wheel truck I2, negative battery wire 96, closed pressure switch 440 and wire 68 back to the negative terminal of the battery 64.

Upon the energization of its magnet winding 43, the magnet valve section 42 of the slip-controlled valve device 36 operates to close the communication through which fluid under pressure is supplied from the pipe 35 to the pressure chamber at one side of the operating piston of the relay valve section M and at the same time establish a communication through which fluid under pressure is rapidly exhausted from such pressure chamber. The relay valve section 4I accordingly operates to effect a rapid reduction of the pressure in the brakecylinders I5 associated with the wheels of the wheel truck I2.

The direction of flow of current through the holding winding 12 of the slip relay 53d is in a direction to maintain the contact of the relay in its closed position independently of variations of the current energizing the pick-up winding a thereof in response to subsequent variations in the rate of deceleration and acceleration of the slipping wheels. Accordingly, the circuit for energizing the magnet winding 43 of the slip-controlled valve device 36 remains established as long as the pressure switch 441 remains in its closed position, which it does until the fluid pressure in the brake cylinders I5 associated therewith is reduced by operation of the slip-controlled valve device 36 to a pressure below five pounds per square inch. At such time the circuit for energizing the magnet winding 43 of the slip-controlled valve device36 is interrupted and the magnet valve section 42 restored to its normal position to interrupt the exhaust of fluid under pressure from the pressure chamber of the relay valve section 4| and reestablish the supply communication from the pipe 35 thereto.

Due to the rapid and prompt release of fluid under pressure from the brake cylinders I5 of the truck having the slipping wheels, the slipping wheels promptly cease to decelerate and begin to accelerate without having reduced in speed to a locked or non-rotative condition. The slipping wheels norm-ally begin to accelerate back toward a speed corresponding to car speed, in response to the reduction of pressure in the brake cylinders, before the pressure switch 441- opens. If for some reason, such as sticking of the brake shoes to the wheels, the brakes are not promptly released in response to the operation of the slip relay 53d, the continued reduction of the pressure in the brake cylinders to below five pounds per square inch positively insures the ultimate release of the brakes and the consequent restoration of the slipping wheels to a speed corresponding to vehicle speed.

The time required for the pressure in the brake cylinders to be reduced below five pounds per square inch of course varies with the pressure established in the brake cylinder but, in any case, the time ordinarily elapsing between the initiation of the wheel-slip and the restoration of the slipping wheels to a speed corresponding to car speed will be less than the time required to reduce the pressure in the brake cylinders to below five pounds per square inch. It will thus be seen that since the opening of the pressure switch 441 and the consequent restoration of the slip-controlled valve device 36 to its normal position for re-supplying fluid under pressure to the brake cylinders I5 does not occur until after, or substantially at the time the slipping wheels are restored fully to the speed corresponding to car speed, the reapplication of the brakes on the slipping wheels will not be effected while the wheels are slipping. Thus the likelihood that the Wheels will again slip due to reapplication of the brakes on the slipping wheel is minimized.

It will be apparent that due to the venting of the pressure chamber of the relay valve section 4i of the slip-controlled valve device 36 in response to the slipping of the wheels, the restoration of the slip-controlled valve device 36 to its normal condition to eiiect resupply of fluid under pressure thereto tends to effect a reduction of the pressure in the pipe 35. The speedcontrolled valve mechanism 21, however, is operative through the relay valve section 28 thereof to maintain a pressure in the pipe 35 which is that percentage of the pressure in the control pipe I5 corresponding to the particular speed range in which the vehicle is traveling. The slip-controlled valve device 36 is, therefore, operated upon the opening of the pressure switch 441* to resupplyfluid under pressure to the associated brake cylinders I5 at a pressure corresponding to the particular speed range in which the car is traveling. v

If the slipping of the wheels was caused by a momentary bad rail condition,that is low adhesion condition of the rails, the restoration of the usual pressure to the brake cylinders for the particular speed range following slipping of the wheelswill not cause repeated slipping of the wheels. If, however, the low adhesion condition of the rails continues so that upon restoration of fluid under pressure to the brake cylinders following wheel slip slipping of the wheels again occurs, the above operation is repeated. Thus at no time during an application of the brakes are the wheels permitted to decelerate to a locked or nonrotative condition and slide.

' It will be seen that because the contact of the slip relay 530 is connected in parallel with the contact of the slip relay 53d, the slipping of the wheels of the leading wheel unit of the wheel truck I2 will result in operation of the slipcontrolled valve device 36 for the rear wheel truck I2 in the same manner as just described. In this connection, it will be noted that the relay 530 does not have its Winding b connected in the circuit for energizing the magnet winding 43 of the slip-controlled valve device 36 for the rear wheel truck I2. However, the winding b of the slip relay 5311 is energized by closure of the contactof the slip relay 53c and the contact of the relay 53d is therefore actuated to its closed position. Thus, once the circuit for energizing the magnet winding 43 of the slip-controlled valve device 36 for the wheel truck I2 is established by the contact of the slip relay 53c, the subsequent drop-out of the relay 530 is immaterial because the circuit is thereafter maintained by the contact and self-holding winding 17 of the relay 53d.

It is possible to arrange the winding b of the relay 53c and its contact in series relation just as is the contact and winding 1) of the relay 53d so that the relay 530 may, independently of the relay 53d, maintain the circuit for energizing the magnet winding 43 of the slip-controlled valve device 35.. However, in the event that the wheels associated with both the trailing and the leading wheel units of truck l2 slip at the same time, it is possible that due to the parallel arrangement of the windings b of the two relays 53c and 53d insufficient current would be sup plied to energize these windings to maintain the contact members of the relays in their closed positions. The arrangement which I have pro vided whereby only one of the pair of slip relays for a given wheel truck has its holding winding 11 arranged in the circuit for energizing the magnet winding 43 of the slip-control valve device 36 insures adequate current to maintain the contact member of at least one of the relays in its closed position until the circuit is interrupted by opening of the pressure switch 441.

If the wheels associated with either the trailing or th leading wheel units of the wheel truck ll begin to slip during an application of the brakes, one or the other or both of the slip relays 53a and 53bare picked-up and the contacts thereof accordingly actuated to their picked-up or closed positions to establish a circuit for energizing the magnet winding 43 of the magnet valve section 42 of the slip-controlled valve device 36 -corre-- sponding to the wheel truck II subject to the opening of the pressure switch 44 associated with the brake cylinders of that truck. The circuit for energizing the magnet winding 43 of the slip-controlled valve devices 36 associated with the wheel truck H is sufficiently obvious in view of the previously described circuit for. the magnet winding 43 of slip-controlled valve device 36 for the wheel truck l2 as to obviate the need for specific description thereof. It will be noted that only the winding b of the slip relay 53b is employed as a holding winding in the circuit of the magnet winding 43 of the slip-controlled device 36 for the wheel truck H, for the same reason previously given in connection with the relays 53c and 53d.

('61) Adaptability of equipment for travel of car in either forward or reverse direction In the previously described operation, it was assumed that the vehicle was traveling in a forward direction so that the directional relay 54] and correspondingly the repeater relay 55] were picked-up while the directional relay 541' and repeater relay 551' were dropped-out. If the car is connected in a train in such a manner that the wheels rotate in the opposite direction to that .for the forward travel of the car, which situation is herein referred to as reverse travel of the car, th equipment will operate in exactly the same manner as previously described. It will be apparent that such is the case because the directional relay 541 and correspondingly the repeater relay 551" will be picked-up while the directional relay I 54] and the repeater relay 55 will b droppedout. Thus, the connections of the speed. relays 52L, 52M, and 52H as well as those of the slip relays 53a, 531x530, and 53d will be reversed so that, although the polarity of the brush terminals 49 and 50 of the generators 48 is reversed, that is although they are now of negative and positive polarity, respectively, the bus wires 19 current through the windings a of the slip relays will'be the same as for forward travel; Thus the slip relays will respond only to the rotative deceleration oi the corresponding wheels or wheel units at a slipping rate.

While it has previously been proposed to provide automatic apparatus for automatically reversing the connections of wheel-slip relays of electrical wheel-slip responsive apparatus of the type shown, the arrangement which I have pro-, vided including two directional relays and two directional-repeater relays arranged in interlocked and coordinated relation insures against the possibility of undesired reversed connections for a particular direction of travel. This may be demonstrated by assuming that the directional relay 54 fails to drop-out upon a reversal of polarity of the brush terminals 49 and 50 of the associated generator 8. t will be seen that, in such case, the circuit for energizing the winding 55?" of the directional repeater relay 551' cannot be established due to the fact that the back contact e of the directional relay 54f is open.

It will be apparent also that if either of the directional relays 55,2 and 541 fails to drop-out in proper manner upon deenergization of the windings thereof at the time that thecar comes to a stop, the subsequent reversed flow of current in the circuit of the windings of. the directional relays due to reversed travel causes a force to be exerted tending to positively restore the relay to its dropped-out position. Moreover, if either of the directional relays54f and 541' fails to drop-. out in a proper manner when the car comes to a stop, the continued illumination of the indicating lamp 6! will serve as an indication of this fact to the operator so that he may take the necessary steps to correct the fault before proceeding.

If either of the directional-repeater relays 55f and 551' happens to stick in its picked-up position and. fails to drop out properly in response to the opening of the pressure switch 440 at the time that the brakes are released in the manner press ently to be described, the subsequent pick-up of the other directional-repeater relay will discon nect the generators 48 from and effect a shortcircuiting of the windings a of the slip relays 53b, 53c, 53d so that no undesired operation thereof can occur. It will be seen that when the contacts e, f and g of the two repeater relays 55f and 551" are simultaneously in their pickedup positions, each correspondingly designated pair of contacts short-circuits the winding a of the corresponding slip relay and disconnects the corresponding generator ea.

In the case of the speed relays 52L, 52M, and 52H and the slip relay 53a, the simultaneous pick-up of contacts 0 and d of both the directional-repeater relays 55 and 551 will result in disconnecting the relays from the generator 48, in a manner readily apparent, although the relay windings are not short-circuited.

It will thus be seen that by means of the novel arrangement of the two directional relays 541 and 541' and directional-repeater relays 55f, BET, it is practically impossible to secure improper operation of the equipment due to reversed travel.

(e) Release of brakes sure in the control pipe, I6 is accordingly vented toatmosphere through the exhaust port and pipe 25 at the brake valve II. The speed-controlled valve mechanism 21 operates in response to thereduction of pressure in the control pipe I6 to vent fluid under pressure from the pipe 35 and correspondingly from the relay valve section 4| of th slip-controlled valve devices 36 to atmosphere through the exhaust port of the relay valve section 28. The slip-controlled valve devices 36, in turn, operate to vent fluid under pressure from the brake cylinders I5 through the exhaust port of the relay valve sections M. The brakes are accordingly completely released in response to the exhaust of fluid under pressure from the brake cylinders I5. The pressure switches 44 and 441 associated with the brake cylinders are accordingly restored to their open position. The pressure switch 440 is likewise restored to its open position in response to the reduction of the pressure in the control pipe I6 to atmospheric pressure.

The restoration of the pressure switch 440 to its open position interrupts the electrical circuits for all of the various relays and magnet valves except, of course, the directional relays 54f and 541. Accordingly, it is impossible for current to be drained from the storage battery 64 as long as the brakes are released except in accordance with the demands of lighting circuits which may be supplied therefrom and which are not shown.

It is to. be noted that the energizing circuit for the indicating lamp 6I is independent of the pressure switch 440 so that the operation of the indicating lamp is independent of the condition of the pressure switch 440. Obviously, as previously indicated, if the two directional relays 541 and 541' both drop-outin their intended manner indicating lamp 6| will be extinguished when the car approaches a stop.

Although the directional relays 541" and 54f may drop out while the car is still traveling at a speed of four or five miles per hour, the directional-repeater relays 55f and 551" are not dropped-out correspondingly until the pressure switch 440 opens. Since the brakes are not completely released until after the car has come to a complete stop, it will therefore be apparent that the short-circuit connection including the series-related condenser I05 and winding a of each of the slip relays 53b, 53C, and 53d effected by contacts 6, f, and y of the directional-repeater relays 551 and 551' when both of these relays are simultaneously dropped-out will not be established at a time the vehicle is in motion. The possible pick-up of the slip relays 53b, 53c, and 53d due to the momentary discharge of the condensers I05 associated therewith when one or the other of the directional-repeater relays 55f or 551" is restored to its dropped-out position may be effective to cause operation of the slip valve devices 35 to release fluid under pressure from the brake cylinders at this time. However, since the brakes are, in any case, being released this is an advantage rather than a disadvantage; Of course, once the pressure switch 440 opens due to reduction of pressure in control pipe I6,the slip-controlled valve devices will be restoredto their normal condition due to interruption of the electrical circuits by pressure switch 440.

In the case of the slip relay 53a, the restoration of one or the other of the directional-repeater relays 55] or 551' to its dropped-out position does not establish a short-circuit connection around the winding a of the relay 53a and the associated condenser I05 and, consequently, no discharge flow of current through the winding a sufficient in degree to cause pick-up of the contact member of this relay can occur] The condenser I05 associated with the relay 53a will in such case discharge through the circuit including the parallel connected windings a of the speed relays 52L, 52M, and 52H. The resistance of this circuit is so high however that the current discharged from the condenser will be insufficient to cause pick-up of the slip relay 53 (f) Adaptation of equipment to a train of connected units or cars In the case of a train of connected units or cars, either of the non-articulated or of the articulated type, the control of the brakes on all the units or cars by the operator is effected solely through the medium ofthe control pipe- I6 which extends from car to car and which is controlled by a brake Valve similar to the brake valve II on one or more of the cars. As previously indicated, if each of the cars is provided with a brake valve II, those brake valves on the cars other than the power car on which the operator is stationed may be cut-out of operation by means of the manually operated valves 24 in the branch pipes leading to the brake valves.

While I have for simplicity shown a supply pipe I9 as extending from car to car throughout the train, it will be apparent that each individual unit of the car may be provided with an independent fluid pressure supply system including a fluid compressor and associated reservoir corresponding to the main reservoir I8. In such case, no connection between the sections of the supply pipe I9 on successive cars need be made.

The generators 43 associated with the wheels on all the units or cars will be identical indesign and consequently produce substantially uniform voltages for a corresponding speed of rotation of the vehicle wheels. Accordingly, the speed-controlled valve mechanisms 21 on the different units or cars will be automatically controlled in synchronism so as to reduce the degree of application ofthe brakes on all cars in unison as the speed of the train reduces.

If for some reason, such as unequal wear of the wheels of different cars, and the consequent difierence in diameter of the wheels, the voltage produced by the generators on different cars varies somewhat, thespeed-controlled valve mechanisms 21 on different cars may not operate exactly in synchronism. However, such fact is not considered objectionable because of the fact that when any of the critical speed. ranges is traversed and another speed range entered, the consequent change in the condition of the speed controlled valve mechanism does not result in a rapid adjustment of the pressure in the brake cylinder but rather an adjustment at a controlled rate so thatthe reduction from one degree of pressure to another effected by the valve mechanism 2'! is not instantaneous. Accordingly, even if the speed controlled valve mechanisms 21 on different cars are not operated exactly in synchronism, the difference in the pressure of the brake cylinders on different cars will not vary by a substantial amount and consequently undesired slack action in the case of a train of non-articulated cars, will not occur. In the case of articulated cars, where no slack action can occur the fact that the brakes associated with the wheels of one unit may be braked a little more or a little less than those on another unit of the car is unobiectionable; I I

a S MMARY ,7

Summarizing, it will be seen that I 'have'disclosed anovel brake control equipment adapted to a single car .or a train of cars of either the non-articulated or the articulated type in which the operator located at a control station on one of the cars, such as a power car or loco-motive, may control the brakes on all the cars uniformly and in which each individual unit or car is provided with apparatus'forautomatically decreasing the degree of application of the brakes independently of the operator in accordance with the reduction of speed of the car and for causing a rapid reduction in the degree'of application of the brakes associated with individual-wheel units or groups-of wheel units intheievent that any of the wheels of that group begin to slip, so as to cause the slipping wheels to be restored to a speed'corresponding to car speed without causing sliding thereof. I

The speed-control equipment for each car comprises, according to my invention, a plurality of sive relaysare provided with-a holding coil separate from the pick-up coil thereof, and a selfholding contact which, when pickedeup in, reg sponseto operation of the relay, establishes a circuit for energizing amagnet valve device which causes a rapid reduction of the pressure in the brake cylinders associated with the slipping wheels and, a t the same tima sets up the holding circuit for the holding coil of the relay to prevent the drop-out of the relay until suchtime as the pressure in the brake cylinder is reduced below a certain low pressure.

In view ofthe speed relaysand slip relays being pair of so-called directional relaysand a pair ofdirectional-repeater relays for reversing the connections of the speed relaysand slip relays to the generators associated with the corresponding wheel unit so as to insure the unidirectional flow of current through the pick-up coils of the speedrelays, and in the case of: the slip relays, uni-directional "flow "toitne pick-up coils: of the relays for deceleration of the wheels.

The directional control apparatus which I have provided is one of the features of my'inv'ention and is adapted'to prevent theundesired operationor improper operation of any of the speed r'elay's'or wheel slip relays due to'a change in polarity of generators associated with the vehicle wheels resulting from a reversal of travel of the car. The arrangement of the directional control apparatus is such as to normally maintain "the circuits, on which the slip relays and speed relays operate, open so that the generators associated with the wheel units are normally unloaded and sothat such circuits are established only during a brake application.

' of the uni-directional type, I"' have provided a a assent It should be understood-that the herein-dc scribed arrangement for insuring positive operation of the relays 52L, 52M and 52I-I-at critical control voltages is claimed in this application only in connection with'brake control apparatus. The arrangement is more broadly claimed without reference to brake control apparatus in my copending applications, Serial No. 361,929 and Serial No. 395,907, filed October 19, 1940, and May 31, 1941, respectively.

While I have shown and described only one specific embodiment of my invention, it will be apparent that various omissions, additions, or modifications may be made in the equipment withoutdeparting from the spirit of my invention, asfor example the provision of speed-con trol apparatus only, wheel-slip control apparatus only, orth provision of speed-control apparatus and wheel-slip control apparatus for one wheel unit only of a particular group'of wheels or wheel units. 7 7

It is accordingly not my intention to limit the scope of my invention except in accordance with the terms of the appended claims.

Having now described my invention, whatl claim as new and desire to secure'by Letters Patent, is:

1. Brake control apparatus for -a hicle comprising, in combination, manually controlled means for establishing aicontrol pressure variable according .to a desired degree of applicationiof the brakes, relay valve means effective in one condition thereofin response to argiven control pressure to cause application of the brakes associated with the vehicle wheels to one degree andeffective in response to said given control pressure in another condition thereof to cause application of the brakes associated with the vehicle wheels to a different degree, means for supplying a direct-current voltage substantially'proportional'to thelrate of rotative-speed of a vehicle wheel and of opposite polarity for opposite directions'of rotation of said wheeLan electrical relay having an operating winding on whichthe voltage supplied by the voltage supply means is impressed and a movableelement which is operativelyv actuated to-and maintained in .an operated position only so long as a voltage of one certain polarity and exceeding a certain value is impressed on the operating'winding of the relay, means controlled according to the polarity of they voltage supplied by. the voltage supply means for reversing the connections between the operating winding of the relay andsaid voltage supply'means so that a voltage of, the said one certain polarity is impressed on thejopera-ting winding of said relay whether the said wheel is rotating in onedirection or the opposite direction, and means controlled according to the position of the control element of said relay for causing said relay valve means to be conditioned in its said one condition or its said diiierent condition, whereby to vary the degree of application of the brakes dependent upon the speed of rotation of the vehicle Wheel and accordingly the speed of travel of the vehicle.

2. Brake control apparatus for a wheeled vehicle comprising, in combination, manually controlled means for establishing acontrol fluid pressure variable according to a desire degree of application of the brakes, relay valve means adapted to be variously conditioned in any one of ,a plurality of different conditions and operative in response to a given control fluid pressure to establish difi erent degrees of application of thebra'kes wheeled ve- 

